244 



FRESH-WATER BIOLOGY 



lo(ii) Pseudopodia ray-like with swellings along their course. Flagella 



directed forward . Acinetactis Stokes. 



Representative species Acinetactis mirabilis Stokes 1886. 



Body subsphcrical, soft, and plastic. Short, lobate pseudopodia 

 often in addition to capitate rays. Flagella subequal arising at 

 some distance from each other. Nucleus central; contractile vacu- 

 oles two. Diameter about 1 2 m- Stagnant pond water. 



Fig. 364. Acinetactis mirabilis. X 700. (After Stokes.) 



11(10) Pseudopodia lobe-like. Flagella two, one trailing. Cercobodo Kvaas. 

 Representative species Cercobodo sp. 



Species not determined. 



Fig. 365. Cercobodo sp. X 1250. (After Conn. 



12 (5) Plastic but not forming pseudopodia. Flagellum single. 



Family Cercomoxadidae 



13 



13 (14) With a posterior tail-like filament Ccrcomonas Dujardin. 



Representative species. . . Cercomonas longicaudata DuisLvdm 1S41. 



Body elongate-ovate, fusiform, terminating 

 posteriorly in a long, tail-like filament about 

 c o twice the length of the body. Nucleus spher- 



ical, subcentral. Length 10 fx. Vegetable 

 infusions. 



Fig. 366. Cercomonaslongicaudata. a;, contractile 

 vacuole; », nucleus X 1200. (After Stein.) 



14 (13) Without a tail-like filament Oikomonas Kent. 



Representative species Oikomonas steinii Kent 1880. 



Body, in motile condition, exceedingly plastic with a single 

 flagellum at the anterior end and a lip-like extension which as- 

 sists in taking food; in sedentary state, pyriform and attached 

 by posterior extremity. Nucleus posteriorly located. Length,- 

 when contracted, about 20 to 30 tx. Vegetable infusions. Social. 



Fig. 367. 



Oikomonas steinii. cv, contractile vacuole; n, nucleus. 

 X 440. (After Blochmann.) 



